Conventionally, as a method of improving image quality of a video signal, enhance processing to improve a feeling of sharpness of a video is performed by attaching a shoot component to an edge of a video signal to make the edge steep. An enhancer that performs this enhance processing is a device that extracts a high frequency component of a video signal using a high pass filter having a comparatively short tap length of several to ten and several taps, generates a shoot component based on the extracted high frequency component, and attaches the shoot component to the video signal. In Patent Document 1, such an enhancer (image quality improving device) is described.
Here, it is described that the high frequency component is extracted by the high pass filter. However, in practice, there is a case where intermediate and high frequency components including an intermediate frequency component are extracted and the intermediate and high frequency components are emphasized. When the peak frequency of the passband of the high pass filter is shifted toward an intermediate frequency side, the intermediate and high frequency components are emphasized. Further, when the gain is increased in order to improve the effect of emphasis of the high frequency component, the intermediate frequency component is extracted accompanying the high frequency component. As a result, the intermediate and high frequency components are emphasized. Hereinafter, explanation is given on the assumption that the conventional enhancer emphasizes the high frequency component even when it emphasizes, in fact, the high frequency component including the intermediate frequency component.